The endosymbiotic bacterium Wolbachia is widely recognized for its potential as a vehicle to introduce disease-resistance genes into mosquitoes, making them refractory to the human pathogens they transmit. This is due to its ability to induce a reproductive abnormality known as cytoplasmic incompatibility (CI). CI is early embryo death when a Wolbachia infected male mates with a female that is uninfected or harboring a different Wolbachia type. Since uninfected males can successfully mate with infected females, Wolbachia and any gene it carries can spread quickly in a population. First discovered in the Culex mosquito, CI is the only phenotype known to be induced by Wolbachia in mosquito. Although different models has been developed to interpret the CI mechanisms, the molecular base for CI is not yet elucidated. We had successfully generated a stable Wolbachia infection in an Aedes aegypti line. Due to the ability of Wolbachia to induce the complete CI in this line and the availability of whole genome sequence in Ae. aegypti, this Wolbachia/mosquito association provides us an ideal system to dissect the CI mechanism. Our long term goal is to understand the cross talk between Wolbachia and its host which results in the occurrence of CI. Our central hypothesis is that CI is induced by a change in the expression of genes involved in spermatogenesis in testes and embryogenesis in ovaries. Our project has three specific aims: 1) Construct an in silico Wolbachia-mosquito protein interactions network. We will predict Wolbachia-mosquito protein interaction network by computation methods based on protein domain profiles and sequence homology. 2) Define the response of mosquito genes in reproductive tissues to Wolbachia infection. We will use microarray to compare the gene expression in ovaries and testes between Wolbachia-infected and uninfected mosquitoes. 3) Identify host factors that determine CI expression. We will knock-down the putative host CI genes by RNA interference and test their impact on CI expression. This research is innovative because it is the first study of the CI mechanisms at the systems biological and functional genomic level. The successful completion of this project will uncover host factors that determine CI, which can be used for further identification of their interaction partners in Wolbachia. Our anticipated findings would also contribute directly to the current effort to improve the Wolbachia-based transgene driver system to spread genes capable of blocking the transmission of mosquito-borne pathogens. PUBLIC HEALTH RELEVANCE: Our anticipated findings would aid in the development of the improved genetic methods to block the transmission of mosquito-borne infectious diseases, including malaria, dengue fever and West Nile.